Thermoelectric air conditioner

ABSTRACT

A thermoelectric unit including thermoelectric modules, cold side fins, a heat sink, a hot side heat absorption element, and an electronic controller. The heat absorption element includes a metal heat transfer structure, phase change material (PCM) and heat exchange medium.

FIELD OF THE INVENTION

The present invention relates generally to thermoelectric airconditioning systems, particularly for temperature control of a confinedspace.

BACKGROUND OF THE INVENTION

Thermoelectric devices utilize the properties of certain materials todevelop a thermal gradient across the material in the presence ofcurrent flow. For example, thermoelectric devices may utilize P-type andN-type semiconductors as the thermoelectric material within the device.These are physically and electrically configured in such a manner thatthey provide cooling or heating.

SUMMARY OF THE INVENTION

The present invention seeks to provide a novel thermoelectric airconditioner/dehumidifier (thermoelectric air conditioner, for short) foroperating inside a confined space (such as, but not limited to, aprotective suit, sealed enclosure, closed room, and many others) withoutexternal power source, as is described more in detail hereinbelow.

The thermoelectric unit comprises, without limitation, thermoelectricmodules, cold side fins, heat sink, with or without fans, hot side heatabsorption element, electronic controller and battery.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a simplified illustration of a thermoelectric air conditioner,constructed and operative in accordance with an embodiment of thepresent invention.

FIG. 2 is a simplified illustration of gas (e.g., air) used as the heatexchange medium in the thermoelectric air conditioner, in accordancewith an embodiment of the present invention.

FIG. 3 is a simplified illustration of liquid (e.g., water or nanofluid)used as the heat exchange medium in the thermoelectric air conditioner,in accordance with an embodiment of the present invention.

FIG. 4 is a simplified illustration of a thermal insulating portion madeas a multilayer cover with one or more layers of PCM as middle layers,in accordance with an embodiment of the present invention.

FIG. 5 is a simplified illustration of a thermal insulating portionbetween cold and hot portions of the air conditioner, in accordance withan embodiment of the present invention.

FIG. 6 is a simplified illustration of the cold heat sink containing atank for condensed water collection, in accordance with an embodiment ofthe present invention.

FIG. 7 is a simplified illustration of the air conditioner having a tube(tubes) for cold air distribution, in accordance with an embodiment ofthe present invention.

FIG. 8 is a simplified illustration of the tube (tubes) filled withgranular PCM, in accordance with an embodiment of the present invention.

FIG. 9 is a simplified illustration of PCM granules inserted inside thecold side heat sink, in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is now made to FIG. 1, which illustrates a thermoelectric airconditioner (unit) 10, constructed and operative in accordance with anembodiment of the present invention.

The thermoelectric unit 10 includes, without limitation, thermoelectricmodules 12, cold side cooling fins 14, a cold side heat sink 16 with orwithout a fan 18, hot side heat absorption element 20, electronictemperature controller 22 and a power source (e.g., battery) 24, allinside a confined space (referred to as a sealed enclosure) 26.

The heat absorption element 20 includes a metal heat transfer structure21, phase change material (PCM) 23 and a fluid heat exchange medium 25.The PCM 23, without limitation, is in the form of granules with lengthdimensions of 3-5 mm and content of PCM inside the granule at least 70%.The invention is not limited to these values.

The PCM 23 can have a single working temperature or can be composed of amixture of materials with different working temperatures.

The heat transfer structure is preferably made from materials with highthermal conductivity of at least 200 W/m/K, such as some aluminumalloys.

Without limitation, the heat transfer structure 21 can be of thefollowing types:

-   -   Plane fins with fins thickness of 0.5-3 mm and distance between        the fins of (1-3)*D, where D size of PCM granule    -   Pin fins with pin thickness of 1-4 mm and distance between the        pins of    -   Foam structure with relative porosity of 50-90% and cell        dimension of (2-6)*D

The heat exchange medium 25 can be air, water, nanofluid and others. Thenanofluid can include PCM nano-particles with the same workingtemperature as the PCM granule or a mixture of nanoparticles withdifferent working temperatures.

When air is used as the heat exchange medium 25, fans or blowers 30 canbe used to improve heat exchange between the PCM granular and heattransfer structure, as seen in FIG. 2.

In order to ensure sufficient heat exchange rate at appropriate power,the input power of the fans (blowers) air flow rate inside the heattransfer structure 21 should be in the range of 1-3 m/s.

When water or nanofluid or other liquid is used as heat exchange medium25, a pump 32 can be used to enhance heat exchange (FIG. 3). To ensuresufficient level of heat transfer liquid at appropriate pressure levels,the liquid flow rate should be in the range of 1-101/min.

In FIG. 4, the heat absorption element 20 includes a thermal insulatingportion 34 to prevent heat losses to the surrounding space. To ensureminimum thermal losses thermal insulating portion 34 is made asmultilayer cover with one or more layers of PCM 23 as middle layers.

The working temperature of the PCM layers should be an average value ofthe working temperature of PCM (granular and nanofluids) inside the heatabsorption portion and enclosure air temperature.

In FIG. 5, the thermal insulation 34 between cold and hot portions ofthe air conditioner is made as multilayer material with one or moremiddle layers of PCM 23. The working temperature of the PCM layer(s) 23should be chosen between the temperatures of the hot and cold portionsof the air conditioner.

In order to prolong operation of battery, the cold heat sink can containPCM with a temperature equal to or lower than the enclosure airtemperature.

Due to the fact that temperature of the cold side heat sink surface islower than the enclosure air temperature, the air conditioner canoperate as a dehumidifier.

The electronic temperature controller 22 maintains temperature of thecold heat sink required to reach the specified humidity inside theenclosure.

In FIG. 6, the cold heat sink 16 can include a tank 36 for condensedwater collection.

In FIG. 7, the cold portion of the air conditioner (with fins 14) cancontain manifold tubing 40 for cold air distribution (FIG. 7). Themanifold tubing 40 can be made from flexible plastic material, allowingdirection of cold air flow to desired points. The tubing 40 can be madefrom rigid material with a permanent shape to provide constant air flowdistribution.

In order to prolong battery operation and to stabilize output airtemperature, the tubing 40 can be filled with granular PCM 23 (FIG. 8).

The working temperature of PCM can be equal to or lower than the airconditioner output temperature. The size of PCM granules should be inthe range: (0.2-0.8)*d, where d is the inside diameter of the tubes.

PCM granules 23 can be also inserted inside the cold side heat sink 16or fins 14 (FIG. 9). After operating the air conditioner, PCM partsshould be reloaded. The electronic controller provides the function ofreloading by reverse operation of the air conditioner. During reverseoperation, the former hot portion is cooled and the former cold portionis heated. Reloading of the air conditioner is performed together withbattery recharging by connecting to the external power source.

1. Apparatus comprising: a thermoelectric unit comprising thermoelectricmodules , cold side cooling fins, a cold side heat sink, a hot side heatabsorption element, and an electronic temperature controller, whereinsaid heat absorption element comprises a metal heat transfer structure,a phase change material (PCM) and a fluid heat exchange medium which isa liquid.
 2. Apparatus according to claim 1, wherein said PCM comprisesgranules with length dimensions of 3-5 mm.
 3. Apparatus according toclaim 1, wherein said PCM has a single working temperature.
 4. Apparatusaccording to claim 1, wherein said PCM comprises a mixture of materialswith different working temperatures.
 5. Apparatus according to claim 1,wherein said heat absorption element comprises a thermal insulatingportion to prevent heat losses to surrounding space.
 6. Apparatusaccording to claim 5, wherein said thermal insulating portion comprisesa multiple layers with one or more layers of PCM as middle layers. 7.Apparatus according to claim 1, wherein said cold heat sink comprises atank for condensed water collection.
 8. Apparatus according to claim 1,further comprising manifold tubing for cold air distribution. 9.Apparatus according to claim 1, wherein said fluid heat exchange mediumcomprises a nanofluid.
 10. Apparatus according to claim 9, wherein saidnanofluid comprises PCM nano-particles with the same working temperatureas the PCM.
 11. Apparatus according to claim 9, wherein said nanofluidcomprises a mixture of nanoparticles with different workingtemperatures.
 12. Apparatus according to claim 1, further comprising apump for pumping said liquid.